Optimization of Cutting Parameters during Dry Turning of Austenitic Stainless Steel Using nc-AlTiN/Si3N4, TiAlN, and TiN Coated Inserts

The nc-AlTiN/Si3N4, TiAlN, and TiN coating were deposited using lateral rotating cathodes (LARC) technology on TNMG 160404 cemented carbide turning inserts. Ultrafine grain treated cemented carbide substrates were used in case of TiAlN and TiN inserts. The coated inserts were tested for their hardness and compositions were determined by X-ray diffraction studies. The grain structures of coatings were observed using scanning electron microscopy. Dry cutting tests were performed on AISI 304 stainless steel to compare the performances of these coatings in terms of wear and surface finish imparted to workpiece. 3D confocal laser microscope was used to determine the flank wear. Grey relation analysis was carried out to optimize the machining parameters. Studies reveal that nc-AlTiN/Si3N4 coating showed the highest hardness of 28 GPa. The coating also shows a dense grain structure. Furthermore, in cutting tests even under severe dry cutting conditions, the wear observed was less than the other two coatings and surface finish imparted to work parts was less than 2 μm by this coating.